When building a conventional doorframe for pivotally installing a door within the doorframe, the doorframe should be pre-erected in a construction site and then, the concrete is formed or the bricks are stacked around the doorframe to fix the doorframe with the concrete or brick wall.
However, it has the following drawbacks:
1. The doorframe is pre-erected in the construction site by strut or brace or linkage, which may obstruct the construction or material handling by the workers.
2. The doorframe pre-erected in the site may be easily scratched, impacted, worn, twisted, deformed or damaged during the construction of the building or house.
3. The doorframe is supplied as a fixed doorframe set already fabricated in a factory, thereby lacking of diversity, flexibility or adjustment for the construction.
The present inventor has found the drawbacks of a conventional doorframe and invented the present knockdown doorframe and its building method.